1. Field of the Invention
The present invention is related to an automatic analysis apparatus and a dispensing method for the same analyzing components contained in a liquid.
2. Description of the Related Art
An automatic analysis apparatus measures a change in color or the like generated in a mixed liquid of a test specimen and a reagent by utilizing a transmission quantity of light, etc. The analysis apparatus analyzes densities of a variety of substances to be tested and activities of enzymes in the test specimen on the basis of the measurement result.
The analysis apparatus presets analysis conditions such as a quantity of the test specimen and the reagent, a reaction time of the mixed liquid or a wavelength of the light, etc., to be used for the measurement for each measurement item, and further selects to set measurement items to be measured for each test specimen before starting the measurement. The analysis apparatus measures the measurement items selected for each test specimen in relation to each of a large number of test specimens.
As for the measurement, a random access system and a semi-random access system have been well known. The semi-random access system can perform processing at a speed higher than that of the random access system. The semi-random access system is known, for instance, by Jpn. Pat. Appln. KOKAI Publication No. 9-101313.
In the random access system, the a specimen is dispensed from a specimen vessel into reaction vessels by using one probe corresponding to one measurement channel (also called measurement line) for each analysis cycle. Then, a reagent appropriate for the measurement item selectively set in advance is dispensed from the reagent vessel into the reaction vessels with the test specimen dispensed therein by using a reagent dispensing probe corresponding to the measurement channel.
The semi-random access system further includes a multiple item dispensing system and a single item dispensing system. The multiple item dispensing system aspirates the test specimen for a plurality of measurement channels at once by one probe. The multiple item dispensing system then divides the test specimen from the probe to infuse it to a plurality of reaction vessels each corresponding to the plurality of measurement channels. The single item dispensing system infuses the test specimen held in one specimen vessel at the same time by a plurality of probes each corresponding to the plurality of measurement channels. The single item dispensing system then infuses the test specimen from the plurality of probes to the plurality of reaction vessels each corresponding to the plurality of measurement channels, respectively.
By the way, the automatic analysis apparatus aspirates the test specimen to the probe and infuses the test specimen therefrom by aspirating and infusing a pressure transferring medium such as water sealed in a tube through the probe and a pump connected by the tube. The test specimen aspirated by the probe is sometimes contacted with the pressure transferring medium and diluted by the transferring medium near by the contact point. Therefore, the analysis apparatus is so constituted as not to infuse the test specimen diluted by the transferring medium to the reaction vessels by aspirating the test specimen of a volume larger than that of infusing to the reaction vessels. The test specimen aspirated by the probe but not infused to the reaction vessels is called a dummy.
In the multiple item dispensing system, since a large volume of test specimen is aspirated in the probe at once and a plurality of times of infusion operations are repeated, a mixture of the test specimen and the pressure transferring medium is apt to be caused in the probe, and there is a risk that even the test specimen infused to the reaction vessels is diluted by the transferring medium. Therefore there is a risk of a reduction in precision, for instance, in analyzing an immunity item of an extremely low density, so that the single item dispensing system is preferable for achieving an analysis with high precision.
However, in the single item dispensing system, the probe and pump, etc., of the same number as that of the measurement channels being required, an automatic analysis apparatus results in becoming complex and expensive.